The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 2002-217733, filed on Jul. 26, 2002. The contents of that application are incorporated herein by reference in their entirety.
1. Field of the Invention
The invention relates to a steering control system for a vehicle, especially for an automobile.
2. Description of the Related Art
In a steering apparatus for a vehicle, especially a power steering apparatus for an automobile, it is developed a variable gear ratio system changing a converting ratio of a steering angle from a handle operation angle according to a driving stage of the vehicle without fixing the converting ratio to 1:1. The driving stage is detected by a vehicle speed, for example. During a high speed driving, it is possible for the driving to be stabilized by preventing the steering angle from being large rapidly according to an increasing of the handle operation angle by the way of decreasing the converting ratio at the high speed driving. On the other hand, during a low speed driving, to increase the converting ratio of the steering can decrease a handle rotation to reach an end of the steering angle so that it is easy for a driver to drive in a large steering angle operation such as a parking or a column parking.
It is well known for the variable gear ratio system to directly couple a handle shaft and a steering shaft by a gear transmission device with a variable gear ratio disclosed in, for example, the Japan laid-open publication No. 11-334604. This construction has a defect of a complex in the gear change mechanism of the gear transmission device. It is well known for the variable gear ratio system to separate the handle shaft and the steering shaft by the way of driving the steering shaft by an actuator such as a motor and so on disclosed in, for example, the Japanese laid-open publication No. 11-334628. A computer of this system calculates the steering angle finally needed according to the handle operation angle detected by an angle detector and the converting ratio of the steering angle, and controls to drive the actuator or the motor for the steering shaft separated mechanically from the handle shaft in order to get the calculated steering angle.
In the well known steering control system, a precise monitoring of an angular position of the steering shaft is needed. The detection of the angular position is performed by an angle sensor such as a rotary encoder and so on. It is used for counting a pulse output to detect an absolute angular position in an incremental encoder. The counting is performed by sampling the encoder pulse at predetermined interval to add or decrease one in the counter according to receiving one pulse therein. However, it is happened to rotate the encoder accordingly to two pulses in sudden acceleration of the motor by a rapid handling or a shock. The counter counts only one pulse in one sampling even though in this sudden situation so that an accuracy of detecting the angle deteriorates to cause the incorrect steering angle control.
In view of the previously mentioned circumstances, it is an object of the present invention to provide a steering control system for a vehicle increasing an accuracy of detecting an angular position.
It is second object of the present invention to provide a steering control system for a vehicle increasing an accuracy of detecting an angular position by the way of eliminating a counting by sudden rotation of a steering motor.
It is third object of the present invention to provide a steering control system for a vehicle performing correctly an angle identifying operation of an angular position of steering shaft according to a motor rotation number.
In order to achieve the above and other objects, the present invention provides a steering control system for a vehicle comprising at least an angle detector and a steering controller. The steering controller identifies a rotational direction of the angle detector based on a pattern output, performs a sampling of the pattern output at a predetermined interval, identifies an order of combination order of the identified pattern of an angle phase in a first sampling and a second sampling following to the first sampling, and determines a pattern exchange number with the rotational direction. The steering controller adds a number corresponding to the pattern exchange number to a counting number when the rotational direction is plus and decrease a number corresponding to the pattern exchange number from the counting number when the rotational direction is minus. The steering controller has an angular position counter of steering shaft registering said angular position of steering shaft by the counting number. In the present invention, the detection of the angular position of steering shaft is performed by the angle detector or sensor identifying the phase of a rotation angle of the shaft based on the identified pattern of the angle phase. For example, the angle sensor has a rotatable member formed the identified pattern of the angle phase in the predetermined combination order at the same interval. In the present invention, the angle sensor is constructed to be able to be read the angle phase by the kind of the pattern exchange and to be used the counting number as the angle position of steering shaft. This is a kind of use of the incremental angle sensor, however, the present invention can perform the angle detection unenforceable by the well known angle sensor. When the sampling of the detected pattern of the angle phase is performed at neighboring pattern, it is possible for the angle sensor to detect an advancing number or retracting number in the order of the formed pattern to identify the rotational advancing angle generated in the angle sensor at the sampling interval by the pattern exchange number. Therefore, in the present invention, it detects the pattern exchange number and an exchanging direction from the order of the first sampling to the order of the second sampling, and it adds the number corresponding to the pattern exchange number to the counting number when the rotational direction is plus and decreases the number corresponding to the pattern exchange number from the counting number when the rotational direction is minus. Thereby, when the angle sensor is rotated in more than two patterns at only one sampling by the sudden acceleration of the motor caused by a rapid handling or a shock, the angle sensor can add or decrease in the counter according to the pattern exchange number to be able to detect the angular position precisely to increase the accuracy of the angle control.
It happen a suddenly large rotation of the motor by the shock against a steering control in the driving to generate a disorder of the rotation of the steering shaft independently from the handle operation. The disorder should be eliminated at the identification of the angular position of steering shaft for the accuracy of the steering control. The second aspect of the invention is that the steering controller of the present invention includes a counter control means performing an prohibiting operation prohibiting the operation of adding or decreasing said pattern exchange number to or from the counting number in the angular position counter of steering shaft when an absolute number of the pattern exchange number is larger than a reference pattern exchange number. The function of the counter control means can eliminate the suddenly large advancing angle as abnormality to make the high accuracy of the angle position of steering shaft.
It is not abnormality to make a large motor rotation velocity at the rapid handling and to advance the angle phase corresponding to the motor rotation at the sampling interval. In this occasion, to perform the count prohibiting operation happens to make a decreasing the accuracy of the angular position of steering shaft. The third aspect of the present invention is that the steering control system has an angle velocity detecting member to calculating an angle velocity of a rotatable member of the angle sensor and the counter control means changes a set condition being set to perform the count prohibiting operation according to the calculated angle velocity. Thereby, the count prohibiting is performed at any time according to the motor rotation number to perform correctly the angle identifying operation of the angular position of steering shaft according to the motor rotation number. It can set a large reference pattern exchange number performing the count prohibiting operation according to the large angle velocity.